1. Field of the Invention
The present invention relates to a novel stainproofing agent containing a certain specific polyfluoroalkyl group-containing compound as an active ingredient and a process for its preparation.
2. Description of the Prior Art
Heretofore, in the treatment of fiber products such as woven fabrics or carpets with a treating agent having a polyfluoroalkyl group (hereinafter referred to as a "PFA group"), it has been common to employ a method wherein the treating agent is coated on the surface of the fiber product by means of an aqueous emulsion or organic solvent solution of an acrylate-type high molecular weight polymer. However, such a high molecular weight treating agent constitutes a non-continuous phase held on the fiber surface mainly by physical adhesive power, and consequently tends to be abraded off when the fibers are subjected to mechanical actions during the processing to a final product or during the use as the fiber product. Further, the high molecular weight treating agent having a PFA group has a deficiency in its effectiveness to impart a stainproofing property such as an anti-dry soil property which is important particularly for the treatment of carpets.
There have been proposed various means to overcome the above-mentioned deficiency of the high molecular weight treating agent. For instance, it has been proposed to use as a treating agent a low molecular weight fluorinated compound composed of a derivative of e.g. phthalic acid, terephthalic acid, trimellitic acid or pyromellitic acid. (See U.S. Pat. Nos. 3,646,153, 3,870,748 and 4,209,610.) Further, as a material useful as a stainproofing agent for e.g. carpets, various fluorine-containing urethane compounds having PFA groups have been proposed, for instance, in U.S. Pat. No. 3,398,182 and Japanese Unexamined Patent Publications No. 112,855/1978 and No. 74,000/1979.
The present inventors have now found that a relatively low molecular weight compound obtained by reacting e.g. a PFA group-containing alcohol to a trifunctional isocyanate compound, effectively overcomes the deficiencies of the above-mentioned high molecular weight treating agent and is superior in its abrasion durability to a low molecular weight fluorinated compound such as the conventional fluorine-containing urethane compound. Such a specific compound has a molecular weight of from 800 to 3000 and contains at least three urethane bonds or urea bonds as well as at least one PFA group. Such a PFA group-containing specific compound may be used prior to the dyeing step and is also advantageously be used as a treating agent at the time of spinning base yarns for fiber products such as carpets. The specific treating agent of the present invention is capable of providing a stainproofing property when used at the time of spinning and will not fall off from the fiber products even during the dyeing step and does not adversely affect the dyeing.